Abrasive backing and method of making same

ABSTRACT

An abrasive backing is generally provided. In some embodiments, the abrasive backing includes a base sheet, comprising wood fibers, synthetic fibers, cellulose filaments, a saturant, wherein the saturant includes two or more latex polymers and a crosslinking agent, and a first surface and opposing second surface, a barrier coating adjacent the first surface of the base sheet, and a backside coating adjacent the opposing second surface of the base sheet. A method of producing an abrasive backing is also provided.

FIELD AND BACKGROUND

The present disclosure relates to an abrasive backing with improvedstrength properties.

When using an abrasive backing for sanding applications, a commonproblem is the tearing of the backing after a certain number of sandingcycles. It is also a common issue that after a certain number of folds,the backing tears and is no longer usable. When abrasive backings areused for sandpaper on power equipment, a high amount of internal heatbuildup can negatively impact the rate of material removal when usingthe equipment. Additionally, sandpaper is softened or rejuvenated inwater to wash the sanded material out of the grit and in doing so, thesandpaper loses some of its strength properties from being soaked orcleaned.

Thus, there is a need for an abrasive backer that has improved strengthproperties. Specifically, there is a need for an abrasive backer thatallows for an increased number of sanding cycles or folds before thebacking tears. There is also a need for an abrasive backer thatincreases the rate of material removal and retains its strengthproperties when soaked or cleaned.

SUMMARY

An abrasive backing is generally provided. In some embodiments, theabrasive backing includes a base sheet, comprising wood fibers,synthetic fibers, cellulose filaments, a saturant, wherein the saturantincludes two or more latex polymers and a crosslinking agent, and afirst surface and opposing second surface, a barrier coating adjacentthe first surface of the base sheet, and a backside coating adjacent theopposing second surface of the base sheet. The barrier coating can beimpervious to liquid water and allow transmission of gas. In someembodiments, the abrasive backing can have two or more barrier coatingsapplied adjacent the first surface of the base sheet. The abrasivebacking can have grit applied adjacent to the surface of the barriercoating opposing the first surface of the base sheet. The backsidecoating can be waterproof. In further embodiments, the abrasive backingcan have a layer including a plurality of loops or a plurality of hookson a surface of the backside coating opposing the second surface.

In some embodiments, the base sheet can include wood fibers that includehardwood fibers, softwood fibers, or a combination thereof. In someembodiments, the base sheet can include wood fibers in the base sheetthat include a blend of softwood fibers and hardwood fibers, forexample, a blend of 30-70% softwood fibers and 70-30% hardwood fibers byweight, each based on the weight of the wood fibers and the cellulosefilaments in the base sheet. The base sheet can further include jutefibers, straw fibers, cotton fibers, hemp fibers, bagasse fibers, bamboofibers, reed fibers, sisal fibers, abaca fibers, kenaf fibers, flaxfibers, or a combination thereof.

In further embodiments, the base sheet can have two or more latexpolymers in an amount of from 55% to 99.9% by weight of the saturantbased on the weight of the dry solids in the saturant. In someembodiments, the two of the two or more latex polymers can becrosslinkable. The saturant can include a third latex polymer. The twoor more latex polymers can include copolymers prepared from monomersincluding styrene and butadiene. In some embodiments, the latex polymersare selected from latex polymers having a Tg of from −40° C. to −20° C.and a Tg of from −12° C. to 8° C. The latex polymers can further includea latex polymer having a Tg of 32° C. to 52° C. The latex polymers caninclude 10% to 50% by weight of a latex polymer having a Tg of from −40°C. to −20° C., 50% to 90% by weight of a latex polymer having a Tg offrom −12° C. to 8° C., and 10% to 50% by weight of a latex polymerhaving a Tg of 32° C. to 52° C., based on total dry weight of the latexpolymers. In further embodiments, the saturant can include thecross-linking agent in an amount of from 0.25% to 1.5% by weight of thesaturant based on the weight of the dry solids in the saturant. Thecross-linking agent can include an aziridine crosslinking agent, aglyoxal-based crosslinking agent, ammonium zirconium carbonate, acarbodiimide, an aliphatic polyglycidyl ether,hexamethoxymethylmelamine, zinc diethyldithiocarbamate, or a combinationthereof. For example, the crosslinking agent can include an aziridinecrosslinking agent.

In some embodiments, the base sheet can include cellulose filaments inan amount of from 1% to 5% by weight based on the weight of the woodfibers and the cellulose filaments in the base sheet. The cellulosefilaments can have an aspect ratio of from 200 to 5000 and a width offrom 30 to 500 nm. Further, the base sheet can have synthetic fibers offrom 2% to 8% by weight based on the weight of the wood fibers and thecellulose filaments in the base sheet. The synthetic fibers can includepolyester fibers such as polyethylene terephthalate (PET) fibers. Theabrasive backing can have a basis weight of 75 to 155 gsm.

Methods are also generally provided for forming an abrasive backing. Inone embodiment, the method includes providing a base sheet comprisingwood fibers, synthetic fibers, cellulose filaments, and a saturantcomprising two or more latex polymers and a crosslinking agent, applyinga barrier coating to a first surface of the base sheet, and applying abackside coating to a second surface of the base sheet opposing saidfirst surface of the base sheet. The method may also include providing abase sheet made of wood fibers, synthetic fibers, and cellulosefilaments, saturating the base sheet with a saturant comprising two ormore latex polymers and a crosslinking agent, and drying the saturatedbase sheet. The method may also include providing a base sheet byforming a base sheet from a fiber matrix comprising wood fibers,synthetic fibers, and cellulose filaments, and drying the base sheet.The base sheet can then be calendered after saturating the base sheetwith a saturant. The method of making an abrasive backing can includethe other features described above with regard to the abrasive backing.

The details of one or more embodiments are set forth in the descriptionbelow and accompanying drawing. Other features, objects, and advantageswill be apparent from the description and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

The application includes reference to the accompanying figures, inwhich:

FIG. 1A shows an exemplary abrasive backing; and

FIG. 1B shows an expanded view of the exemplary abrasive backing of FIG.1A along line 1B.

FIGS. 2A and 2B provide data from the examples demonstrating theabrasive backing described herein.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present invention.

DETAILED DESCRIPTION

The present disclosure generally provides an abrasive backing, as wellas methods of its formation. In certain embodiments, the abrasivebacking includes a base sheet comprising wood fibers, synthetic fibers,cellulose filaments and a saturant, wherein the saturant includes two ormore latex polymers and a crosslinking agent. The base sheet includes afirst surface and an opposing second surface. Adjacent the first surfaceof the base sheet is a barrier coating and adjacent the opposing secondsurface is a backside coating.

Referring to FIG. 1A, an exemplary abrasive backing 10 is shown, formedfrom a base sheet 12 having a first surface 11 and a second surface 13.A barrier coating 22 is adjacent the first surface 11 of the base sheet.A backside coating 20 is adjacent the second surface 13 of the basesheet 12.

FIG. 1B illustrates an expanded view of the abrasive backing 10 of FIG.1A. In the embodiment shown, the base sheet 12 includes a plurality offibers including softwood fibers 14, hardwood fibers 16, and syntheticfibers 24. The base sheet 12 also includes cellulose filaments 26. Thebase sheet 12 also includes latex particles 18 that are provided fromthe two or more polymers in the saturant.

Each of the components of the abrasive backing 10 provided herein isdiscussed in greater detail below with respect to the abrasive backingand the method of forming the abrasive backing.

The base sheet 12 includes a plurality of fibers that includes woodfibers, synthetic fibers, and cellulose filaments that are boundtogether by a polymeric matrix formed by the reaction of the two or morelatex polymers and the crosslinking agent. As discussed herein, thepolymeric matrix is provided by the saturant that saturates theplurality of fibers in the base sheet. In some embodiments, the hydroxylgroups present in the fibers and the cellulose filaments can hydrogenbond with pendant groups present in the latex polymers provided in thesaturant (for example, when the latex polymers are carboxylated).

The wood fibers in the base sheet can include softwood fibers 14,hardwood fibers 16, or blends thereof. In certain embodiments, the woodfibers can include a blend of softwood and hardwood fibers. The basesheet can include 5-95%, 10-90%, 20-80%, or 30-70% softwood fibers byweight based on the weight of the wood fibers and the cellulosefilaments in the base sheet. The base sheet can include 5-95%, 10-90%,20-80%, or 30-70% hardwood fibers by weight based on the weight of thewood fibers and the cellulose filaments in the base sheet.

Examples of softwood fibers include Northern Bleached Softwood Kraft(NBSK) and examples of NBSK are provided in Table 1. In someembodiments, the softwood fibers can have a length weighted averagefiber length from 1.99 to 2.30 mm. Examples of hardwood fibers includeNorthern Bleached Hardwood Kraft (NBHK) and examples of NBHK areprovided in Table 2. In some embodiments, the hardwood fibers can have alength weighted average fiber length from 0.58 to 1.11 mm. In someembodiments, it is also possible to substitute a Eucalyptus BleachedKraft (EuBK) for NBHK.

TABLE 1 Properties of Suitable Northern Bleach Softwood Kraft (NBSK)Pulps from 2005 3rd Edition - The World of Market Pulps - ISBN0-615-12861-0 NBSK Arithmetic Length Wtd. Example and Avg. Fiber Avg.Fiber Arithmetic Fiber WOMP Length Length Avg. Fines Population Pulp #Type (mm) (mm) (%) (fibers/mg) I - Pulp #7 Canada/Eastern Slope 1.1532.19 31.76 6,013 II - Pulp #8 Canada/Northern 1.034 2.28 39.90 6,083Plains III - Pulp #9 Canada/Ontario 1.060 2.19 35.18 6,047 IV - Pulp #10Canada/Quebec 1.192 2.30 31.32 5,883 V - Pulp #11 Canada/Maritime &0.907 1.99 37.32 8,025 New England VI - Pulp #13 Scandinavia 1.047 2.2036.03 5,736

TABLE 2 Properties of Suitable Northern Bleached Hardwood Kraft (NBHK)and Eucalyptus Bleached Kraft (EuBK) Pulps from 2005 3rd Edition - TheWorld of Market Pulps - ISBN 0-615-12861-0 NBHK or Arithmetic LengthWtd. EuBK Example Avg. Fiber Avg. Fiber Arithmetic Fiber and WOMP LengthLength Avg. Population Pulp # Type (mm) (mm) Fines (%) (fibers/mg) I -Pulp #29 U.S. New England/ 0.423 0.65 34.42 25,588 Mixed HW Species II -Pulp #28 Scandinavia/Birch 0.688 0.91 17.31 13,936 III - Pulp #27Canada/Birch 0.722 1.11 23.93 11,170 IV - Pulp #25 Canada/Aspen 0.5720.75 25.1 18,583 V - Pulp #26 Canada/Maple 0.356 0.58 34.8 36,013

In some embodiments, the plurality of fibers can include additionalfibers. The additional fibers can include jute fibers, straw fibers,cotton fibers, hemp fibers, bagasse fibers, bamboo fibers, reed fibers,sisal fibers, abaca fibers, kenaf fibers, flax fibers, or a combinationthereof. The additional fibers can replace 1% or greater, 5% or greater,10% or greater, 20% or greater, 30% or greater, or 40% or greater, or50% or greater, or 50% or less, 40% or less, 30% or less, 20% or less,10% or less, or 5% or less by weight of the wood fibers in the basesheet. For example, straw fibers can be used to replace all or a portionof the hardwood fibers that would be used in a hardwood/softwood fiberblend.

The base sheet 12 can include cellulose filaments. The cellulosefilaments can be formed, for example, from unraveling of wood fibers toprovide single filaments. The cellulose filaments can have an aspectratio of from 200 to 5000 and a width of from 30 nm to 500 nm. Oneexemplary source of cellulose filaments is FILOCELL™ CF, which iscommercially available from Kruger Biomaterials Inc. The cellulosefilaments can be provided in the base sheet in an amount of from 0.1% to10%, 0.5% to 7.5%, or 1% to 5% by weight based on the weight of the woodfibers and the cellulose filaments in the base sheet.

The plurality of fibers can include synthetic fibers to provideadditional properties to the base sheet. For example, the syntheticfibers can work in conjunction with the wood fibers to increase the tearresistance of the base sheet. The synthetic fibers can be formed of anysuitable material and to any suitable size and shape as long as theresulting synthetic fibers serve as high tensile strength fibers.Examples of such synthetic fibers can include polyolefins (e.g.,polyethylene, polypropylene, polybutylene, etc.);polytetrafluoroethylene; polyesters (e.g., polyethylene terephthalate);polyvinyl acetate; polyvinyl chloride acetate; polyvinyl butyral;acrylic resins (e.g., polyacrylate, polymethylacrylate,polymethylmethacrylate, etc.); polyamides (e.g., nylon 6, nylon 6/6,nylon 4/6, nylon 11, nylon 12, nylon 6/10, and nylon 12/12); polyvinylchloride; polyvinylidene chloride; polystyrene; polyvinyl alcohol;polyurethanes; polylactic acid; and combinations thereof. In certainembodiments, the synthetic fiber includes a polyester such aspolyethylene terephthalate (PET) 24. Synthetic PET fibers include thosecommercially available from Toray Industries, Inc. In some embodiments,the synthetic fibers have a length from 1 mm to 10 mm or from 2 mm to 8mm. In some embodiments, the synthetic fibers can have a denier of from0.5 dpf (denier per filament) to 6.0 dpf or from 3.0 dpf to 6.0 dpf. Thesynthetic fibers are provided in the base sheet in an amount of from0.5% to 15%, 1% to 12%, 2% to 10%, or 2% to 8% by weight based on theweight of the wood fibers and the cellulose filaments in the base sheet.

Various additives can be applied to the plurality of fibers duringformation of the fibrous web or after formation of the base sheet 12(e.g., to the dried fiber). For example, wet-strength agents can be usedto improve the strength properties of the web during formation. Thewet-strength agents can be present in an amount from 0.001% to 5% or0.01% to 2% by weight based on the weight of the wood fibers and thecellulose filaments in the base sheet. Wet strength agents are typicallywater soluble, cationic oligomeric or polymeric resins that are capableof bonding with the cellulosic fibers. For example, some suitablewet-strength agents are polyamine-epichlorohydrin, polyamideepichlorohydrin, or polyamide-amine epichlorohydrin resins (collectively“PAE” resins). Other wet strength agents can also be employed in certainembodiments. For example, other suitable wet strength agents can includedialdehyde starches, polyethyleneimines, mannogalactan gum, glyoxalresins, polyisocyanates, and dialdehyde mannogalactan. In someembodiments, the wet-strength resin includes a polyamide-epichlorohydrin(PAE) resin.

Various other additives can also be employed in the base sheet 12. Theadditives can be provided with the fibers during formation of the basesheet or applied to the base sheet with the saturant. Suitable additivescan include antifoaming agents, processing aids, surfactants, anddispersing agents. For example, kaolin pigments can be included in thebase sheet to increase opacity. A wide range of pigments and dyes canalso be added to impart color to the base sheet. Pigments and dyes canbe added during formation of the base sheet, can be provided with thesaturant when the base sheet is saturated, or can be provided as aseparate coating onto the base sheet after saturation.

As discussed herein, the plurality of fibers are provided in a polymericmatrix in the base sheet 12. The polymeric matrix is provided by asaturant or saturating composition that is used to saturate the fibersin the formation of the base sheet or after the base sheet is formed. Incertain embodiments, the saturant is provided after the base sheet isformed by saturating the base sheet. As discussed herein, the polymericmatrix is formed by the use of at least two latex polymers and acrosslinking agent. In certain embodiments, two or more of the at leasttwo latex polymers are crosslinkable so they can react with thecrosslinking agent or with other latex polymers in the saturant. Thereaction of the latex polymers and the crosslinking agent can occurthrough heat or by the removal of water from the saturant in the basesheet. In addition to physically bonding the plurality of fibers in thebase sheet, one or more of the latex polymers and the crosslinking agentcan additionally bond with the plurality of fibers or the cellulosefilaments, for example, through hydrogen bonding.

The saturant includes at least two latex polymers 18, at least threelatex polymers, or more. In some embodiments, the saturant includesthree latex polymers. In some embodiments, two or more of the latexpolymers are crosslinkable to form a polymeric matrix when reacted withthe crosslinking agent. In some embodiments, all three of the latexpolymers are crosslinkable. Suitable latex polymers include styrenebutadiene copolymers (formed primarily from the reaction of styrene andbutadiene monomers), styrene acrylic copolymers (formed primarily fromthe reaction of styrene and (meth)acrylic and/or (meth)acrylatemonomers), pure acrylic copolymers (formed primarily from the reactionof (meth)acrylic and/or (meth)acrylate monomers), or mixtures thereof.For example, the pure acrylic copolymer can be a polyacrylate salt suchas a zinc polyacrylate. Other suitable latex polymers includeN-methylolacrylamides, ethylene-vinyl acetate copolymers, nitrilerubbers, acrylonitrile-butadiene copolymers, poly(vinyl chloride)copolymers, poly(vinyl acetate) copolymers, ethylene-acrylatecopolymers, vinyl acetate-acrylate copolymers, neoprene rubbers ortrans-1,4-polychloroprenes, cis-1,4-polyisoprenes, butadiene rubbers,cis- and trans-1,4-polybutadienes, ethylene-propylene copolymers, ormixtures thereof. In certain embodiments, the latex polymers can becrosslinkable and can include functionalized groups configured to allowcrosslinking of the latex polymer either with the crosslinking agent,another latex polymer, or both. For example, the latex polymer caninclude crosslinkable groups such as carboxyl groups, amine groups,pyridyl groups, or combinations thereof. In some embodiments, thecrosslinkable latex polymers can include one or more carboxylatedstyrene butadiene copolymers. In some embodiments, the particle size ofthe latex polymer particles can range from 100 nm to 300 nm or from 140nm to 210 nm.

In some embodiments, the saturant can include the two or more latexpolymers 18 in an amount of from 55% to 99.9% or 70% to 99.75% by weightbased on the weight of the dry solids in the saturant. The at least twolatex polymers can include latex polymers having a Tg of from −40° C. to−20° C. and latex polymers having a Tg of from −12° C. to 8° C. Incertain embodiments, the latex polymers can have a Tg of from 32° C. to52° C. For example, the latex polymers can include 10% to 50% by weightof a latex polymer having a Tg of from −40° C. to −20° C., 50% to 90% byweight of a latex polymer having a Tg of from −12° C. to 8° C., and 0%(or 10%) to 50% by weight of a latex polymer having a Tg of from 32° C.to 52° C. based on total dry weight of the latex polymers in thesaturant. Certain properties can be imparted to the base sheet 12 byusing different polymeric latexes depending on the particle size, gelcontent, glass transition temperature, and number of crosslinking groups(e.g., the degree of carboxylation).

The saturant can include a crosslinking agent. In certain embodiments,the crosslinking agent can include an aziridine crosslinking agent, aglyoxal-based crosslinking agent, ammonium zirconium carbonate, acarbodiimide, an aliphatic polyglycidyl ether,hexamethoxymethylmelamine, zinc diethyldithiocarbamate, or a combinationthereof. In certain embodiments, the crosslinking agent can include anaziridine crosslinking agent. The saturant can include the crosslinkingagent in an amount of from 0.1% to 2.5%, 0.2% to 2%, or 0.25% to 1.5% byweight based on the weight of the dry solids in the saturant. Acrosslinking agent with an aziridine backbone achieves both wet and dryproperties as it covalently bonds with molecules having carboxylic acidgroups, such as carboxylated styrene butadiene latex, thereby forming acrosslinked network.

Other components can be included in the saturant composition, asdesired. For example, an antioxidant compound can be included in thesaturating composition. Antioxidants help inhibit oxidation of thesaturating composition during the curing process. Oxidation can discolorthe saturating composition and degrade its final physical properties.Examples of antioxidants include substituted phenolic compounds such asbutylated dihydroxyanisole, di-tert-butyl-p-cresol, and propyl gallate.Additional examples of antioxidants include aromatic amines, such as,di-beta-naphthyl-para-phenylenediamine and phenyl-beta-naphthylamine. Ifused, the antioxidants can be included in the formulation at aconcentration of less than 10%, less than 5%, less than 2%, less than1%, or less than 0.5% by weight based on the weight of the dry solids inthe saturant. In one particular embodiment, a phenol-type antioxidantcan be included in the saturating composition.

Additional materials such as fillers, emulsifying agents, waterrepellants, and film forming resins can be included in the saturatingcomposition, if desired. Suitable fillers can include silica orsilicates, clays, and borates. The filler can be included in thesaturant in an amount of greater than 0% to 45% or 5% to 30% by weightbased on the weight of the dry solids in the saturant. The filler (e.g.,a clay) can act to reduce the moisture and air penetration of the basesheet. Examples of suitable clays include No. 1 high brightness kaolinclays, as provided in Table 3, No. 1 High Brightness Ultrafine Clays,No. 2 High Brightness Clays, No. 1 Regular Brightness Ultrafine Clays,No. 1 Regular Brightness Clays, No. 2 Regular Brightness Clays, andcombinations thereof.

TABLE 3 Suitable No. 1 High Brightness Filler Clays from TAPPI TIP0106-06 (2017) Particle Size, % Manu- % Bright- Finer facturer TradeName Solids ness than 2 μm KaMin HYDRAFINE ® 70 90-92 90-94 LLC 90WThiele KAOGLOSS 90 70 90-92 90-94 Kaolin KAOGLOSS 90W 70 90-92 90-94Company Imerys, ASTRA-COTE ™ 70 90 93 Inc.

The saturant can also include other additives for providing thesaturating composition with desirable qualities. Examples can includechemicals for pH adjustment or surfactants. Trisodium phosphate can beincluded in the saturating composition to help control the pH of theemulsion, as an emulsifier, and/or as a thickening agent.

The barrier coating 22 can be applied onto the base sheet 12 followingsaturation. The barrier coating 22 can be applied from a compositionthat can include, independently, any of the materials discussed abovewith respect to the saturant composition. A suitable latex polymericbinder for the barrier coating can include an acrylic latex binder.Suitable polyacrylic latex binders can include polymethacrylates,poly(acrylic acid), poly(methacrylic acid), and copolymers of thevarious acrylate and methacrylate esters and the free acids;ethylene-acrylate copolymers; and vinyl acetate-acrylate copolymers

The latex polymeric binders for the saturant and the barrier coating canbe the same or different. The latex polymer of the barrier coating istypically selected to adhere or bond well to the surface of thesaturated base sheet. Additionally, the latex polymeric binder of thebarrier coating can be configured to flow sufficiently well during anysubsequent calendering (e.g., soft nip calendering or supercalendering).For example, latex polymeric binders having viscosities ranging from10-100 centipoise can be expected to flow sufficiently well.

The thickness of the barrier coating 22 can vary according to theintended use for the resulting adhesive backing. For example, a thinnerbarrier coating can be utilized for coarse grit abrasive products, e.g.,abrasives having particle sizes of 200 mesh or greater (the term “mesh”is used herein to mean U.S. Standard Sieve mesh). On the other hand, athicker barrier coating can be used for finer grit products which are tobe used for polishing or fine surface finishing. A practical minimumlayer thickness is 10 micrometers, whereas the practical maximum layerthickness is 250 micrometers. However, thinner or thicker layers can beemployed, if desired, provided that the layers are continuous.Thermoplastic polymeric compositions which are inherently stiff will bemore useful for coarse grit products, while softer or elastomericthermoplastic polymeric compositions like ethylene-vinyl acetatecopolymers and polyurethanes will be more useful for such fine gritproducts as fine sanding and polishing cloths.

In another exemplary barrier coating, a bond layer can be on the firstsurface and a barrier coating on the bond layer, as disclosed in U.S.patent application Ser. No. 14/245,342 titled “Super Smooth PaperBacking for Fine Grit Abrasives and Methods of Their Application andUse” of Vervacke filed on Apr. 4, 2014, which is incorporated byreference herein.

In certain embodiments, the barrier coating 22 can be impervious toliquid water and allows transmission of gases. In certain embodiments,the barrier coating 22 allows for transmission of gases and liquids. Insome embodiments, the abrasive backing can have two or more barriercoatings applied adjacent to the first surface of the base sheet. Anexemplary abrasive backing can include a make coating applied adjacentto the barrier coating and a grit coating applied adjacent to the makecoating. In some embodiments, the make coating can include a liquidphenolic resole resin, a hydroxyl-bearing polyester, a polyester polyol,an aromatic polyisocyanate, a butyl acetate, a sorbitan laurate, or acombination thereof. In some embodiments, the make coating includes aliquid phenolic resole resin. The make coating anchors the grit to thebase sheet 12 of the abrasive backing 10.

The backside coating 20 can be any suitable layer of or coating on thesecond surface that is not configured to have a layer of abrasiveparticles thereon. Any such backside coating can be utilized andtailored for a specific application, as known in the art. Such abackside coating can be applied from a composition that can include,independently, any of the materials discussed above with respect to thesaturant. In some embodiments, the backside coating 20 can be waterproofand, in some embodiments, can include a layer comprising a plurality ofloops or a plurality of hooks (such as Velcro®). The layer comprising aplurality of loops or a plurality of hooks can be discontinuous and onlybe provided where needed to match with a sanding device that has acorresponding plurality of loops (in the event the backside coating 20has a plurality of hooks) or a plurality of hooks (in the event thebackside coating has a plurality of loops). The backside coating 20 caninclude latex polymers as well as various other additives. Suitableadditives can include antifoaming agents, pigments, processing aids,dispersing agents, and matting agents. In some embodiments, the backsidecoating 20 can include a filler such as diatomaceous earth. Thediatomaceous earth can increase the tactile feel of the backside coating20 when used in hand sanding applications.

An exemplary abrasive backing 10 can be formed from a method thatincludes providing a base sheet 12 comprising wood fibers, syntheticfibers, and cellulose filaments and a saturant comprising two or morelatex polymers and a crosslinking agent, applying a barrier coating 22to a first surface 11 of the base sheet 12, and applying a backsidecoating 20 to a second surface 13 of the base sheet 12 opposing saidfirst surface 11 of the base sheet 12. For certain embodiments of theabrasive backing, providing the base sheet 12 can include providing abase sheet 12 comprising wood fibers, synthetic fibers, and cellulosefilaments, saturating the base sheet 12 with a saturant comprising twoor more latex polymers and a crosslinking agent, and drying thesaturated base sheet 12. In other embodiments, providing a base sheet 12can include forming a base sheet 12 from a fiber matrix comprising woodfibers, synthetic fibers, and cellulose filaments, and drying the basesheet. In some embodiments of the abrasive backing 10, the method offormation can include calendaring the base sheet 12.

In certain embodiments, the abrasive backing 10 is formed by a methodthat includes a barrier coating 22 that is impervious to liquid waterand allows transmission of gases. The method can also include a barriercoating 22 that allows transmission of gases and liquids. There can alsobe two or more barrier coatings 22 applied adjacent to the first surface11 of the base sheet 12. The abrasive backing 10 can also be formed by amethod that includes applying grit adjacent to the surface of thebarrier coating 22 opposing the first surface 11 of the base sheet 12.In some embodiments, the abrasive backing 10 is formed by a method thatincludes a layer comprising a plurality of loops or a plurality of hooksprovided on a surface of the backside coating 20 opposing the secondsurface 13.

In certain embodiments, the abrasive backing 10 includes an abrasivebacking base paper with a basis weight of from 75 to 155 gsm, whichencompasses between A-C weight abrasive papers.

To form the base sheet 12, the plurality of fibers including the woodfibers, the optional additional fibers, the cellulose filaments, and thesynthetic fibers are mixed together. The plurality of fibers isgenerally placed in a conventional papermaking fiber stock prep beateror pulper containing water. The fibrous material stock is typically keptin continued agitation such that it forms a suspension. If desired, thecellulose filaments and/or the wood fibers can also be subjected to oneor more refinement steps to provide a variety of benefits, includingimprovement of the tensile and porosity properties of the base sheet.Refinement results in an increase in the amount of intimate contact ofthe fiber surfaces and can be performed using devices well known in theart, such as a disc refiner, a double disc refiner, a Jordan refiner, aClaflin refiner, or a Valley-type refiner.

The resulting fibrous suspension can then be diluted and readied forformation into a fibrous web using conventional papermaking techniques.For example, the web can be formed by distributing the suspension onto aforming surface (e.g., wire) and then removing water from thedistributed suspension to form the web. This process can involvetransferring the suspension to a dump chest, machine chest, clean stockchest, low density cleaner, headbox, etc., as is well known in the art.Upon formation, the fibrous web can then be dried using any knowntechnique, such as by using convection ovens, radiant heat, infraredradiation, forced air ovens, and heated rolls or cans to produce thebase sheet. Drying can also include centralized steam drying followed bycontact drying. Drying can also be performed by air drying without theaddition of thermal energy.

In some embodiments, the components of the saturant are provided as abeater add so they are present in the fiber suspension used to producethe base sheet. In some embodiments, the saturant can be used tosaturate an already formed base sheet. Any known saturation techniquecan be employed, such as brushing, flooded nip saturation, doctorblading, spraying, and direct and offset gravure coating. For example,the plurality of fibers can be exposed to an excess of the solution andthen squeezed. The squeezing of excess saturant from the plurality offibers can be accomplished by passing the plurality of fibers betweenrollers. If desired, the excess saturant can be returned to the supplyfor further use. After squeezing out excess material, the saturatedplurality of fibers can then be dried. Other suitable techniques forsaturating a plurality of fibers with a saturant are described in U.S.Pat. No. 5,595,828 to Weber and U.S. Patent Application Publication No.2002/0168508 to Reed, et al., which are incorporated herein in theirentirety by reference thereto for all purposes.

The amount of the saturant applied can vary depending on the desiredproperties of the plurality of fibers, such as the desired permeability.Typically, the saturant is present at an add-on level of 10% to 40% byweight, and in some embodiments, from 10 to 25% by weight “parts pickup” or PPU. The PPU add-on level is calculated by dividing the dryweight of the saturant applied by the dry weight of the plurality offibers before treatment and multiplying the result by 100. PPU can becalculated according to the formula:

${PPU} = {\left\lbrack {\left( \frac{BW_{{fiber} + {saturant}}}{BW_{fiber}} \right) - 1.} \right\rbrack \times 100}$

wherein BW_(fiber+saturant) and BW_(fiber) are both bone dry (nomoisture) measurements of the basis weight of the base sheet andBW_(fiber) is the measurement at the stage before the size press andBW_(fiber+saturant) is the measurement after the size press when thesheet has been saturated.

In one particular embodiment, the saturated base sheet 12 is calenderedafter saturation. Calendering the saturated base sheet can increase thesoftness and smoothness of the sheet. When desired, the saturated basesheet 12 can be calendered according to any process. Calenderinggenerally involves pressing the saturated base sheet in a nip formed bya first and second calendering rolls. The effect of calendering on thesaturated base sheet depends upon the temperature, the pressure applied,and the duration of the pressure. For purposes herein, calendering canbe carried out at either ambient or elevated temperatures. Suitablecalendering pressures can be from 50 to 2000 pounds-force per linearinch (pli), 100 to 1600 pli, 300 to 1000 pli, or 400 to 600 pli.Suitable temperatures can be from 20° C. to 240° C., 20° C. to 140° C.,or 20° C. to 90° C.

The duration of calendering can be varied in conjunction with the nippressure and/or the composition of the calender rolls to produce thedesired smoothness of the paper backing for the sheet. For example,softer calender rolls such as fiber-filled rolls tend to compress toform a larger contact area in the nip, thus increasing the duration ofthe calendering. Hard steel rolls compress more, thus decreasing theduration of the calendering. In one arrangement, the calender nipcomprises a steel roll and a soft fiber-filled roll. In anotherarrangement, for example, a production supercalender stack can includemore than two rolls, desirably from nine to eleven rolls, stacked uponeach other in a vertical arrangement. Desirably the stacked rollsalternate between steel and fiber-filled rolls. With such anarrangement, the paper can be exposed to various pressures, up to 1600pli, and a number of nips, for example from one to eight, to develop thedesired smoothness level.

The saturated, calendered base sheet 12 can be dried to remove thesolvent from the saturating composition. For example, the saturated basesheet 12 can be heated to a temperature of at least 100° C., and in someembodiments at least 150° C., such as at least 200° C. Suitable dryingtechniques can include heating with a conventional oven, microwave,forced air, heated roll, can, or thru-air drying. Drying can alsoinclude centralized steam drying followed by contact drying.

Additionally, the saturated, calendered base sheet 12 can be cured suchthat the latex polymer reacts with the crosslinking agent of thesaturating composition to crosslink and form a three-dimensionalpolymeric structure. Thus, the crosslinked latex polymer can help bindthe fibers of the base sheet together, either mechanically and/orchemically.

No matter the particular processing steps of the base sheet, the basesheet 12 is kept at temperatures below that of the softening point ormelting point of the synthetic fibers such that the synthetic fiberskeep their as-laid shape and physical construction in the final plysheet orientation (and resulting abrasive backer laminate). Thus, thestructural and physical integrity of the synthetic fibers is kept intactin the individual ply sheets to allow the synthetic fibers to providestrength properties to the ply sheet.

The backside coating 20 and the barrier coating 22 can be applied to thebase sheet 12. The backside coating 20 can be customized to provideparticular properties. Specifically, the backside coating 20 can beprinted on, can have a tactile feel for hand sanding, or can bepre-coated for pressure sensitive adhesives.

The abrasive backing 10 also has demonstrated improvements of 100% to200% in wet properties, which allows a sandpaper product made of theabrasive backing 10 to retain the strength properties while being soakedor cleaned to wash the sanded material out of the grit. Although notwishing to be bound to a particular theory, it is believed that theimprovements are due to use of a combination of the two or more latexpolymers, the crosslinking agent, the wood fibers, the cellulosefilaments, and the synthetic fibers. The latex polymers providereinforcement to the fibers thereby increasing the strength propertiesand durability of the abrasive backing 10. The improvements in wetsanding properties are also due to the barrier coating and backsidecoating, which decrease the permeability as sheet tightness is improvedwith the use of the saturant.

The abrasive backing 10 can withstand harsh usage in both hand sandingand power tool application in both wet and dry sanding applications. Thestrength improvements in the abrasive backing 10 are exhibited in bothin-plane and out-of-plane strength properties. This is demonstrated by aroot mean square (RMS) tensile index of greater than 95 Nm/g (e.g., from95-100 Nm/g). The out-of-plane delamination force is from 150 gramsforce to 1000 grams force or from 450 grams force to 750 grams force. Itis believed that the cellulose filaments and synthetic fibers provideadditional tear strength by entangling and bonding with the wood fibers.

The abrasive backing 10 has a high delamination force in the wet stateafter both 1 hour or 24-hour soaking cycles, which allows for theabrasive backing to better retain its strength properties after beingsoaked or cleaned. Because the abrasive backing 10 maintains thestrength properties when periodically cleaned in an appropriate polarcleaning solvent like water, the wet sanding longevity is in turnimproved. The improved backing retains 40% to 60% of the dry tensilestrength after a one-hour soak in water. The improved backing does notrequire any increase in refining energy to the base sheet, thereforeallowing for the same level of refining that increased the densificationand strength properties of the backing.

Sandpaper using the improved abrasive backing 10 is more durable in bothhand and power sanding applications. When used in power equipment, theimproved sandpaper will have a reduced internal heat buildup, causingthe energy transfer from the power equipment into the material toimprove. Thus, the rate of material removal will also improve when thesame grit and make coat are applied to the abrasive backing.

The abrasive backing will now be further described by the followingnon-limiting examples. Parts and percentages are on a per weight basisunless noted otherwise.

Test Methods Sample Conditioning

Samples were conditioned using TAPPI T402 sp-13 prior to any of thefollowing test methods with the additional step of pulling conditionedair through the specimens for a minimum of 20 minutes.

Basis Weight

Basis weight was measured using TAPPI T410, however, the specimen wasfour sheets with a total area of 412.3 in² instead of the minimum of 800in.².

Caliper

Caliper was measured using TAPPI T411 om-15.

Tensile Strength, Tensile Energy of Absorption (TEA), Stretch %, and RMSTensile Index

Tensile strength, TEA, and Stretch % were measured using TAPPIT494-om-01. The RMS Tensile is the square root of the MD Tensile squaredplus CD Tensile.

MD Aged Wet Tensile Strength and MD Aged Wet Stretch

MD aged wet tensile strength and MD aged wet stretch were measured usingTAPPI T456 om-15, however, the specimens were aged for 5 minutes at 145°F. before measurement.

Tear

Tear was measured using TAPPI T414 om-21, however, the results are ingrams force to tear sixteen plies instead of one ply.

Gurley Porosity

Gurley porosity was measured using TAPPI T460 using either one sheet orfour sheets.

Wire Smoothness

Wire smoothness was measured using TAPPI T538 om-16.

Delamination

Delamination was Measured Using the Following Procedure:

The Twing-Albert Vantage NX EJA Series testing machine was a properlycalibrated test machine that can be operated in a displacement controlmode with a constant displacement rate of 30.5 cm/min. The testingmachine was equipped with two opposing grips to hold the two ends ofheat seal tape bonded to the abrasive backing specimen. The testingmachine load-sending device was capable of indicating the total loadcarried by the test specimen and in this case a 500N load cell was used.This device was essentially free from inertia lag at the specified rateof testing and indicated the load with an accuracy over the loadrange(s) of interest of within ±1% of the indicated value. The data wasstored digitally and post-processed. At least five specimens were testedper test condition. The accuracy of all measuring equipment hadcertified calibrations that were current at the time of use of theequipment. Specimens were stored and tested at standard laboratoryatmosphere of 23±3° C. and 50±10% relative humidity.

-   -   1. The width of each abrasive backing specimen and heat seal        tape was 15 mm.    -   2. A cloth heat seal tape was laminated at 312° F.±12° F. to        both sides of the abrasive backing by applying the heat seal        tape at a pressure of 45.5 gm/cm² for 20 seconds and was used to        bond opposing sides of the abrasive backing specimen so that the        delamination force was measured along the center plane of the        specimen.    -   3. After the abrasive backing specimen was heat sealed and        before it was loaded into the grip blocks, the delamination was        initiated by hand by pulling the two strips of heat seal tape        away from each other at 180° until at least 2.54 cm was        pre-delaminated.    -   4. The two ends of the heat seal tape on the pre-delaminated        specimen were mounted in the grips of the loading machine,        making sure that the specimen was aligned and centered.    -   5. The specimen was loaded at a constant crosshead rate of 30.5        cm/min.    -   6. The load and displacement values were recorded continuously.    -   7. The test loading was stopped after a test distance of 5.08        cm.    -   8. The specimen was unloaded at a constant crosshead rate of        30.5 cm/min.    -   9. After the specimen was unloaded, the average force in grams        was calculated over the 5.08 cm test distance.

One Hour Wet Delamination

The equipment, test method and instrument parameters were exactly thesame as the Delamination method provided above, except with the additionof a soaking step. Specimens were soaked in an immersion solution of 10g. per liter of a non-ionic surfactant (C₁₄H₂₂O(C₂H₄O)_(n)) for 1 hourprior to testing.

-   -   1. The sample was blotted with paper towels to remove any excess        water.    -   2. The pre-delamination steps and the loading steps as provided        in the Delamination method were performed on the one hour soaked        specimen.    -   3. After the test was completed, the average delamination force        of the one hour soaked specimen was calculated over the 50.8 cm        test distance as performed in the Delamination method.    -   4. The 1 hr. wet delamination force was reported in grams and        the ratio of the one hour wet/dry test was reported as a        percentage.

24 Hour Wet Delamination

Twenty-four hour wet delamination was measured using the same test asthe one hour wet delamination, except that the specimens were soaked inthe immersion solution for 24 hours instead of one hour.

Sheffield Porosity

Sheffield Porosity was measured using TAPPI T547 om-18.

Felt Smoothness

Felt smoothness was measured using TAPPI T538 om-16.

Felt Gloss

Felt gloss was measured using TAPPI T480 om-15.

Turpentine Penetration

Turpentine Penetration was Measured Using the Following Test:

-   -   1. Xylene was combined with heptane at a volume ratio of 3 to 1        and 0.25 g of Sudan Red IV was added per 400 ml of total        xylene/heptane to create a solvent.    -   2. This solvent was brushed on the barrier coat side of the        sample with a 2″ wide paint brush.    -   3. The sample sat for 10 seconds while coated with solvent and        was then wiped off.    -   4. The level of penetration was the rate on a scale of 1, 3, or        4, wherein 1 represents the least amount of penetration and 4        represents solvent penetration to the side opposite the barrier        coat.

Density

Density was calculated by using basis weight as measured above andcaliper as measured above.

EXAMPLES Example 1

Eight different samples of coated, saturated base sheet were preparedand then the properties compared between the samples. For each of theprepared samples, the same process was performed, but the materials usedin both the base sheet and saturant were altered. The samples of coated,saturated base sheet were prepared according to the following method:

Unsaturated base sheets with compositions according to Table 4 wererefined for 15 minutes.

TABLE 4 Description Control A Base Sheet B Northern Bleached 50% 54.6%Softwood Kraft (NBSK) Northern Bleached 50% 43.4% Hardwood Kraft (NBHK)Cellulose Filaments 0   2% (FILOCELL ™ CF) Polyethylene Terephthalate 5%   3% (PET) Fibers Polyamide-Epichlorohydrin 3 g added 3 g added perWet Strength Resin per beater beater

The dried sheets were saturated to the appropriate pickup with saturantsof a composition according to Table 5.

TABLE 5 B O P Q Saturating Saturating Saturating Saturating FormulaFormula Formula Formula Materials (Dry) (Dry) (Dry) (Dry) CarboxylatedStyrene 90 180 130 130 Butadiene Copolymer A (T_(g) of −2° C.)Phenol-Type 0.4 0.4 0.4 0.4 Antioxidant Carboxylated Styrene 90 0 50 50Butadiene Copolymer B (T_(g) of 42° C.) Carboxylated Styrene 20 20 20 20Butadiene Copolymer C (T_(g) of −30° C.) High Brightness 60 30 30 0Kaolin Clay Hyper Platy Kaolin 0 0 0 30 Clay with an 80:1 Aspect Ratio.Styrene Maleic 4.6 4.6 4.6 4.6 Anhydride Water Repellant 1.6 1.6 1.6 1.6(SUNSIZE 137 from Sun Chemical) Trisodium Phosphate 5 0 3 3 Aziridine 02 2 2 Crosslinking Agent Total: 271.6 238.6 241.6 241.6

Barrier and backside coatings were provided on opposing sides of thebase sheet with compositions according to Table 6.

TABLE 6 Barrier Backside Coating Coating (Dry) (Dry) CarboxylatedStyrene Butadiene 200 Copolymer D (T_(g) of 0° C.) Styrene Acrylic LatexBinder (T_(g) 130 of 29° C.) High Brightness Kaolin Clay 60 120.7Carboxylated Styrene Butadiene 212 Copolymer B (T_(g) of 42° C.)Dispersing Agent (SOLSPERSE ® 0.8 40000 available from Lubrizol)Diatomaceous Earth Matting 100 Agent Tan Pigment Dispersion 12.7

Properties for the different abrasive backings are provided in FIGS. 2Aand 2B.

As shown in FIGS. 2A and 2B, there are improved properties whencomparing control samples A_B30 and A_B35 with the abrasive backingsprovided herein. For example, there is an increase in root mean square(RMS) tensile index from approximately 80 Nm/g in A_B30 to a range ashigh as 95-100 Nm/g as shown in samples B_P30 and B_P35. This shows theabrasive backing can withstand harsh usage in both hand sanding andpower tool application in both wet and dry sanding applications. Thereare also 15% to 30% improvements in strength properties such as in-planetensile strength and tear and 100% improvement in out of planeproperties such as z-directional tensile and out of plane delaminationforce on saturated sandpaper product.

The abrasive backing allows for an increased number of sanding cyclesbefore either tensile or tear failure of the abrasive backing. Thisimprovement is demonstrated by the increase in tensile energy ofabsorption (TEA) from 219.8 J/m² in sample A_B30 to 311.9 J/m² in sampleB_P35, as provided in FIG. 2A. This improvement is also demonstrated bythe average fold endurance of 4,194 folding cycles for conditioned andunaged B_35P and the average fold endurance of 6,513 for conditionedB_35P that was aged for 30 minutes at 120° C., as provided in Table 7.

TABLE 7 Conditioned and Unaged Aged 30 min. @ 120° C. Test 1 Test 2Average Test 1 Test 2 Average (folding (folding (folding (folding(folding (folding Sample cycles) cycles) cycles) cycles) cycles) cycles)B_30P 3249 4451 3850 4270 4784 4527 B_35P 4314 4074 4194 7007 6018 6513

Example 2

The properties of sample B_P35 was tested on a commercial 3.15 meterwide paper machine. This embodiment of the abrasive backing had a basesheet with a composition according to Base Sheet B in Table 4 and asaturant with a composition according to saturating formula P in Table5. The components of the base sheet according to Table 4 were suppliedto the paper machine stock delivery system, formed on the Fourdriniertable, wet-pressed, dried, and saturated with the saturant according toTable 5 at a PPU of 28. The barrier coating was applied commercially onthe 3.15 meter paper machine and has a composition according to Table 6.The backside coating was applied offline to sample B_P35_BC and has acomposition according to Table 6.

The property measurements resulting from the trial are provided in Table8. The property improvements are based on the current correspondingcommercial control grade.

TABLE 8 RMS 1 hr. 1 hr. 24 hr. Tensile Delami- Wet/Dry Wet/Dry Wet/DryIndex nation Tensile Delami- Delami- (Nm/g) (g) (%) nation (%) nation(%) B_P35_BC 98 375 40 80 40 Commercial 83 275 25 30 15 Control(Neenah ® 7759P0 at 115 gsm BW) Improvement  18%  36%  60% 167% 167% inProperties (%)

The property measurements of the abrasive backing sample andcorresponding abrasive backings manufactured by Neenah® PerformanceMaterials and Monadnock Paper Mills, Inc. are provided in Table 9. Thecorresponding abrasive backings were manufactured on a commercial scaleand the data provided is published and publicly available.

TABLE 9 B_P35 2079PO 7394P0 7371P0 7557P0 5702P0 C2434-075 ManufacturerMonadnock Papers Neenah ® Performance Materials Mills, Inc. ApplicationMultiTask ® Wet Wet Wet or Dry sanding or Dry sanding sanding BasisWeight 108.7 100 120 148 110 110 116 (gsm) RMS Tensile 106.1 87.8 77.478.6 93.3 87.2 63.8 Index (Nm/g)

As shown in Table 9, there is improved RMS Tensile Index when comparingsample B_P35 with the corresponding products of Neenah® PerformanceMaterials and Monadnock Paper Mills, Inc. For example, there is anincrease in RMS tensile index from 63.8 Nm/g in the Monadnock PaperMills, Inc. product in Table 9 to 106.1 Nm/g in B_P35. The difference inthe RMS Tensile Index between B_P35_BC in Table 8 and B_P35 in Table 9is due to the backside coating applied to B_P35_BC, which increases itsbasis weight to 115 gsm from the basis weight of 108.7 gsm of B_P35.

The compositions and methods of the appended claims are not limited inscope by the specific compositions and methods described herein, whichare intended as illustrations of a few aspects of the claims and anycompositions and methods that are functionally equivalent are intendedto fall within the scope of the claims. Various modifications of thecompositions and methods in addition to those shown and described hereinare intended to fall within the scope of the appended claims. Further,while only certain representative compositions and method stepsdisclosed herein are specifically described, other combinations of thecompositions and method steps also are intended to fall within the scopeof the appended claims, even if not specifically recited. Thus, acombination of steps, elements, components, or constituents may beexplicitly mentioned herein or less, however, other combinations ofsteps, elements, components, and constituents are included, even thoughnot explicitly stated. The term “comprising”, and variations thereof asused herein is used synonymously with the term “including” andvariations thereof and are open, non-limiting terms. Although the terms“comprising” and “including” have been used herein to describe variousembodiments, the terms “consisting essentially of” and “consisting of”can be used in place of “comprising” and “including” to provide for morespecific embodiments of the invention and are also disclosed. Other thanin the examples, or where otherwise noted, all numbers expressingquantities of ingredients, reaction conditions, and so forth used in thespecification and claims are to be understood at the very least, and notas an attempt to limit the application of the doctrine of equivalents tothe scope of the claims, to be construed in light of the number ofsignificant digits and ordinary rounding approaches.

1.-55. (canceled)
 56. An abrasive backing comprising: a base sheetcomprising wood fibers, synthetic fibers, cellulose filaments and asaturant comprising two or more latex polymers and a crosslinking agent,said base sheet comprising a first surface and an opposing secondsurface; a barrier coating adjacent the first surface of the base sheet;and a backside coating adjacent the opposing second surface of the basesheet.
 57. The abrasive backing of claim 56, wherein the barrier coatingis impervious to liquid water and allows transmission of gases.
 58. Theabrasive backing of claim 56, wherein grit is applied adjacent to thesurface of the barrier coating opposing the first surface of the basesheet.
 59. The abrasive backing of claim 56, wherein the backsidecoating is waterproof.
 60. The abrasive backing of claim 56, wherein alayer comprising a plurality of loops or a plurality of hooks isprovided on a surface of the backside coating opposing the secondsurface.
 61. The abrasive backing of claim 56, wherein the wood fibersinclude hardwood fibers.
 62. The abrasive backing of claim 56, whereinthe wood fibers include softwood fibers.
 63. The abrasive backing ofclaim 56, wherein the wood fibers in the base sheet include a blend ofsoftwood fibers and hardwood fibers wherein the blend comprises 30-70%softwood fibers by weight and 70-30% hardwood fibers by weight, eachbased on the weight of the wood fibers and the cellulose filaments inthe base sheet.
 64. The abrasive backing of claim 56, wherein the two ormore latex polymers comprise from 55% to 99.9% by weight based on theweight of the dry solids in the saturant.
 65. The abrasive backing ofclaim 56, wherein at least two of the two or more latex polymers iscrosslinkable.
 66. The abrasive backing of claim 56, wherein the latexpolymers are selected from latex polymers having a Tg of from −40° C. to−20° C. and latex polymers having a Tg of from −12° C. to 8° C.
 67. Theabrasive backing of claim 56, wherein the latex polymers include 10% to50% by weight of a latex polymer having a Tg of from −40° C. to −20° C.,50% to 90% by weight of a latex polymer having a Tg of from −12° C. to8° C., and 10% to 50% by weight of a latex polymer having a Tg of 32° C.to 52° C. based on total dry weight of the latex polymers.
 68. Theabrasive backing of claim 56, wherein the crosslinking agent comprisesfrom 0.25% to 1.5% by weight of the saturant based on the weight of thedry solids in the saturant.
 69. The abrasive backing of claim 56,wherein the crosslinking agent comprises an aziridine crosslinkingagent.
 70. The abrasive backing of claim 56, wherein the cellulosefilaments comprise from 1% to 5% by weight based on the weight of thewood fibers and the cellulose filaments in the base sheet.
 71. Theabrasive backing according to claim 56, wherein the cellulose filamentshave an aspect ratio of from 200 to 5000 and a width of from 30 to 500nm.
 72. The abrasive backing of claim 56, wherein the synthetic fiberscomprise from 2% to 8% by weight based on the weight of the wood fibersand the cellulose filaments in the base sheet.
 73. The abrasive backingof claim 56, wherein the synthetic fibers comprise polyester fibers. 74.The abrasive backing of claim 56, wherein the abrasive backing has abasis weight of from 75 to 155 gsm.
 75. A method of making an abrasivebacking comprising: providing a base sheet comprising wood fibers,synthetic fibers, and cellulose filaments and a saturant comprising twoor more latex polymers and a crosslinking agent; applying a barriercoating to a first surface of the base sheet; and applying a backsidecoating to a second surface of the base sheet opposing said firstsurface of the base sheet.